Method for forming Ta2O5 dielectric layer by using in situ N2O plasma treatment

ABSTRACT

A method for forming a Ta 2 O 5  dielectric layer by using an atomic layer deposition (ALD) method and an in-situ plasma treatment. The method includes steps of: a) depositing a Ta 2 O 5  dielectric layer on a substrate; b) performing a plasma treatment using N 2 O gas; c) repeating the steps of a) and b) at least one time; and d) annealing the Ta 2 O 5  dielectric layer for the crystallization of the Ta 2 O 5  dielectric layer.

FIELD OF THE INVENTION

The present invention relates to a method for forming a Ta₂O₅ dielectriclayer and, more particularly, to a method for forming a Ta₂O₅ dielectriclayer by using an atomic layer deposition (ALD) method and an in-situplasma treatment.

DESCRIPTION OF THE PRIOR ART

With the increase of integration in a semiconductor device, such as adynamic random access memory (DRAM), a capacitor having high capacitancein a narrow space and superior electrical characteristics of a lowleakage current is needed. In order to meet this need, high dielectricmaterial, such as Ta₂O₅, etc., is used as a dielectric layer.

However, a Ta₂O₅ dielectric layer, which is deposited by a low pressurechemical vapor deposition (LPCVD) method, has a poor step coverage, andthereby the electrical characteristics of such a capacitor are degraded.

To solve the above-mentioned problem, an atomic layer deposition (ALD)method is introduced. In the ALD method, a plurality of mono atomiclayers are deposited, and therefore the step coverage may be improved.

FIGS. 1A to 1D are cross-sectional views illustrating a conventionalcapacitor manufacturing process.

Referring to FIG. 1A, a polysilicon layer 11 is deposited on a substrate10 on which predetermined processes have been completed. Thereafter, anative oxide layer (not shown) is removed by using an HF solution or abuffer oxide etchant (BOE), and then a rapid thermal process (RTP) iscarried out in an NH₃ atmosphere. In case of a semiconductor memorydevice, transistors, plugs and interlayer insulating layers are formedin the predetermined processes.

Referring to FIG. 1B, a Ta₂O₅ dielectric layer 12 is deposited on thepolysilicon layer by using the ALD method and an in-situ O₂ plasmaprocess.

The Ta₂O₅ dielectric layer 12 comprises a plurality of mono atomiclayers 12 ₁ to 12 _(n) repeatedly formed on the polysilicon layer.

Referring to FIG. 1C, the Ta₂O₅ dielectric layer 12 is annealed in an O₂atmosphere in order to crystallize the Ta₂O₅ dielectric layer 12. As anexample, an O₅ plasma treatment is performed to crystallize the Ta₂O₅dielectric layer 12.

Referring to FIG. 1D, a top layer 13 is deposited on the Ta₂O₅dielectric layer 12, thereby forming a capacitor including thepolysilicon layer 11, the Ta₂O₅ dielectric layer 12 and the top layer13.

The above described conventional method for forming a Ta₂O₅ dielectriclayer by using the ALD method and the O₂ plasma treatment has thefollowing problems.

As shown in FIGS. 1B and 1C, carbon remaining sites “A” are generated inthe Ta₂O₅ dielectric layer 12 due to the low reactivity of an O₂.Moreover, oxygen deficiency sites “B” remain in the Ta₂O₅ dielectriclayer 12 due to the low activated energy of the oxygen. Accordingly, theelectrical characteristics of the capacitor are degraded by the leakagecurrent due to the oxygen deficiency sites.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a methodfor forming a Ta₂O₅ dielectric layer capable of improving an electricalcharacteristic of the layer by depositing the Ta₂O₅ dielectric layerwith a plasma atomic layer deposition (ALD) method and an N₂O plasmatreatment.

In accordance with an aspect of the present invention, there is provideda method for forming a Ta₂O₅ dielectric layer, comprising steps of a)depositing a Ta₂O₅ dielectric layer on a substrate prepared in achamber; b) performing a plasma treatment using N₂O gas; c) repeatingthe steps of a) and b) at least one time; and d) annealing the Ta₂O₅dielectric layer for the crystallization of the Ta₂O₅ dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from thefollowing description of the embodiments with reference to theaccompanying drawings, in which:

FIGS. 1A to 1D are cross-sectional views illustrating a conventionalTa₂O₅ dielectric layer manufacturing process; and

FIGS. 2A to 2D are cross-sectional views showing a Ta₂O₅ dielectriclayer manufacturing process in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method for forming a Ta₂O₅ dielectric layer according tothe present invention will be described in detail referring to theaccompanying drawings.

FIGS. 2A to 2D are cross-sectional views showing a Ta₂O₅ dielectriclayer manufacturing process in accordance with the present invention.

Referring to FIG. 2A, a polysilicon layer 21 is deposited on a substrate20 on which predetermined processes have been completed. Thereafter, anative oxide layer (not shown) is removed by using an HF solution or abuffer oxide etchant (BOE), and then a rapid thermal process (RTP) iscarried out in an NH₃ atmosphere. In the case of a semiconductor memorydevice, transistors, plugs and interlayer insulating layers are formedin the predetermined processes.

Referring to FIG. 2B, a Ta₂O₅ dielectric layer 22, consisting of aplurality of mono atomic layers, 22 ₁ . . . 22 _(n) is deposited on thepolysilicon layer 21 of the substrate 20 prepared in a chamber by theatomic layer deposition (ALD) method and in-situ N₂O plasma treatments.Through the in-situ N₂O plasma treatments, the carbon remaining sitesand the oxygen deficiency sites are not generated.

The deposition process of the Ta₂O₅ dielectric layer 22 using the ALDmethod and the in-situ N₂O plasma treatments will now be described inmore detail.

First, a mono atomic Ta₂O₅ dielectric layer 22 ₁ is deposited on thepolysilicon layer 21 at a temperature of 200° C. to 300° C. and at apressure of 0.2 Torr to 1.0 Torr. The Ta(OC₂H₅)₅ gas, which is vaporizedat a temperature of 170° C. to 190° C., is used as a source gas. Afterforming the mono atomic Ta₂O₅ dielectric layer 221, the chamber ispurged with an N₂ gas.

Subsequently, the mono atomic Ta₂O₅ dielectric layer 221 is treated withthe in-situ N₂O plasma treatment. For the in-situ N₂O plasma treatment,an N₂O gas is introduced into the chamber at a rate of 10 sccm to 500sccm and then plasma is generated under an RF power of 30 W to 500 W. Inthe preferred embodiment of the present invention, the in-situ N₂Oplasma treatment is performed at the same temperature and pressurecondition in which the mono atomic Ta₂O₅ dielectric layer 22 ₁ isdeposited, for about 0.1 seconds to 10.0 seconds. After the in-situ N₂Oplasma treatment, the chamber is purged with the N₂ gas.

With the in-situ N₂O plasma treatment, the carbon atoms, remaining inthe mono atomic Ta₂O₅ dielectric layer 22 ₁, react with the oxygen atomsand form CO or CO₂; accordingly, the carbon atoms are removed. Also, theoxygen deficiencies in the mono atomic Ta₂O₅ dielectric layer 22 ₁ arereduced by the N₂O plasma, which has a high active energy.

Thereafter, the deposition of the mono atomic Ta₂O₅ dielectric layersand the in-situ N₂O plasma treatments are performed repeatedly.Accordingly a plurality of mono atomic Ta₂O₅ dielectric layers, forexample 22 ₂ to 22 _(n), are formed on the first mono atomic Ta₂O₅dielectric layer 22 ₁, thereby forming the Ta₂O₅ dielectric layer 22which has a superior step coverage.

Referring to FIG. 2C, the Ta₂O₅ dielectric layer 22 is annealed at atemperature of 650° C. to 800° C. for about 10 minutes to 30 minutes inan N₂O or an O₂ atmosphere to crystallize the Ta₂O₅ dielectric layer 22.

Referring to FIG. 2D, a top electrode 23 is deposited on the Ta₂O₅dielectric layer 22.

As described above, a method for forming a Ta₂O₅ dielectric layer inaccordance with the present invention improves step coverage by forminga Ta₂O₅ dielectric layer through an atomic layer deposition (ALD) methodand an N₂O plasma treatment, and improves the quality of the Ta₂O₅dielectric layer, thereby enhancing an electrical characteristic.

Although the preferred embodiments of the invention have been disclosedfor illustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

1. A method for forming a Ta₂O₅ dielectric layer, comprising: a)depositing a mono-atomic Ta₂O₅ layer on a substrate prepared in achamber; b) performing a nitrogen plasma treatment using N₂O gas plasmaon said mono-atomic Ta₂O₅ layer; c) repeating the steps of a) followedby b) at least one time to form a plurality of mono-atomic Ta₂O₅ layersas a Ta₂O₅ dielectric layer; and d) annealing the Ta₂O₅ dielectric layerin a N₂O gas atmosphere or an O₂ gas atmosphere for crystallization ofthe Ta₂O₅ dielectric layer.
 2. The method of claim 1, wherein the stepsa) and b) are performed in-situ.
 3. The method of claim 1, wherein thestep a) includes the steps of: a1) flowing Ta(OC₂H₅)₅ gas into thechamber; and a2) purging the chamber.
 4. The method of claim 3, whereinstep b) includes flowing the N₂O gas at a rate of 10 sccm to 500 sccm togenerate nitrogen plasma.
 5. The method of claim 4, wherein an RF powerof about 30 W to 500 W is applied to generate the nitrogen plasma. 6.The method of claim 3, wherein the step a1) is carried out at atemperature of approximately 200° C. to 300° C.
 7. The method of claim6, wherein the step a1) is carried out at a pressure of 0.2 Torr to 1.0Torr.
 8. The method of claim 4, wherein the step of flowing the N₂O gasis carried out for about 0.1 to 10.0 seconds.
 9. The method of claim 1,wherein the step d) is carried out a temperature of about 650° C. to800° C.
 10. The method of claim 9, wherein the step d) is carried outfor about 10 minutes to 30 minutes.